Analysis of the relationships between the δ18O from Nevado Illimani and spatial distribution of precipitation over South America

Abstract

This paper examines the relationship between an oxygen 18 isotopic ratio (δ¹⁸O) time series measured in an ice core from Nevado Illimani (Bolivia, 16°37’S, 6°46’W) with the precipitation spatial distribution in South America. For this, we use paleoclimatic data of the upper 50 m of the ice core and 360 layers of instrumental precipitation data between 4°N and 40°S in South America. Precipitation data were grouped by Principal Component Analysis in T-mode and the temporal occurrence of each group (Anomalous Spatial Pattern - ASP) is found when the correlation index between the principal components and the observed precipitations is greater than |0.4|. There are twelve precipitation ASPs, which result mainly from the variability of the surface temperature on the Equatorial Pacific and Tropical North Atlantic oceans. These ASPs temporal occurrence analysis and δ¹⁸O the time series variability indicate that the maximum (minimum) isotopic fractionation in summer is related to droughts (above mean precipitation) in the Amazon or Northeastern region of Brazil. In winter, the maximum (minimum) isotopic ratios are related to droughts (above mean precipitation in the coastal region) in the tropics and above mean precipitation (droughts) in the extratropical region.